The regulation of glycolysis in intact red blood cells and ascites tumor cells is being studied. The hysteretic and mitochondrial-binding properties of tumor hexokinase will be studied. A ribose diphosphate from red cells has been found to activate phosphofructokinase that is inhibited by 2,3-diphosphoglycerate. We will identify the activator, determine if it turns over in the mature red cell, and characterize its mode of action. We will measure 1,3-diphosphoglycerate in red cells maintained at a buffered lactate-pyruvate ratio in aerobic and anaerobic red cells to determine the binding to hemoglobin, using the known phosphoglycerate kinase equilibrium.